From the Guidelines
Laboratory tests for pancreatic neuroendocrine tumors (PNETs) should include chromogranin A (CgA), hormone-specific tests based on clinical symptoms, and other biomarkers such as pancreatic polypeptide, neuron-specific enolase (NSE), and pancreastatin, as recommended by the most recent guidelines 1. The initial testing should include CgA, which is elevated in 60% or more of patients with PNETs, though it has limited specificity. Additional hormone-specific tests should be ordered based on clinical symptoms, such as:
- Insulin and proinsulin with C-peptide for suspected insulinomas
- Gastrin for gastrinomas
- Glucagon for glucagonomas
- Vasoactive intestinal peptide (VIP) for VIPomas
- Serotonin metabolites (5-HIAA) for carcinoid syndrome These tests can help establish diagnosis, determine tumor functionality, guide treatment decisions, and provide baseline values for monitoring disease progression and treatment response. Some key points to consider when ordering these tests include:
- Timing of specimen collection is important, particularly for hormones with diurnal variation
- Some tests require specific preparation such as fasting or medication discontinuation
- Care should be taken in measuring chromogranin A and interpreting the results, because spuriously elevated levels of chromogranin A have been reported in patients using proton pump inhibitors, those with renal or liver failure, those with hypertension, and those with chronic gastritis, as noted in the guidelines 1. Genetic testing is also recommended for patients with suspected hereditary syndromes like MEN1, VHL, or NF1, as suggested by the guidelines 1.
From the Research
Laboratory Tests for Pancreatic Neuroendocrine Tumors (PNETs)
- The diagnosis of PNETs involves specialized diagnostic tests, including laboratory tests to evaluate hormonal secretion 2, 3.
- Chromogranin A is recommended as a general marker for PNETs, but its diagnostic effectiveness remains controversial 4, 5.
- Plasma chromogranin A levels have been shown to be higher in PNET patients than in patients with other tumors, with a sensitivity of 49.2%, specificity of 77.8%, and accuracy of 60.9% for PNET diagnosis 5.
- The diagnostic value of chromogranin A depends on tumor size, with higher sensitivity, specificity, and accuracy for large tumors 5.
- Other serum biomarkers, such as circulating tumor cells, multiple transcript analysis, microRNA profile, and cytokines, are being investigated but are not yet widely used in clinical practice 4.
- Pancreatic hormone testing is critical for the diagnosis and follow-up of functional PNETs, as it can help identify excessive hormonal secretion and action 3.